1. Field of the Invention
The present invention relates to a stapler in which a pusher for pressing a staple is fixed when a driver plate drives the staple toward sheets of paper, thereby reliably driving the staple into the sheets.
2. Background Art
In order to enhance a binding capability of a stapler, generally, it is important to guide both leg portions of a staple so as to be neither inclined longitudinally nor opened transversely when a driver plate drives the staple. The reason is that a buckle occurs when the both leg portions are inclined or bent longitudinally or transversely. For this reason, conventionally, a guide groove is formed in a back side of a face plate so that a U-shape staple is fitted in the guide groove and the both leg portions of the staple are guided so as to be neither inclined in a forward direction nor opened transversely. A guiding operation for preventing the both leg portions of the staple from being inclined backward is carried out by means of a pusher for pushing the staple toward the face plate which is provided in a forward part. The pusher always pushes the staple toward the face plate side by means of a spring. Therefore, the staple is guided so as not to be inclined backward by a force of the spring.
In an electric stapler including a forming plate for forming a straight staple into U-shape, a pusher for pushing the formed U-shape staple toward a driving portion, and a driver plate for driving the staple toward sheets of paper, the U-shaped staple formed by the forming plate is pushed out from a back side by means of the pusher and is thus fitted in a guide groove of a face plate, and both leg portions of the staple are guided to stick at a right angle with respect to a surface of the sheets when the staple is driven out by the driver plate.
Further, the conventional stapler is disclosed, for example, in JP-A-2004-306538.
However, the pusher for guiding a rear part of the staple which is being driven in serves to press and guide the staple by a spring force. If a force for inclining the staple backward is great, therefore, the pusher tends to be moved backward against the spring force. For this reason, a spring load for pushing the pusher in a forward direction is to be increased in order to reliably carry out the guiding operation. If the spring load is increased, however, resistances of the forming plate and the pusher are increased, resulting in a forming failure. For this reason, the spring load cannot be increased. Thus, the pusher is moved away to cause a buckle in some cases.